<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div id="app">
    你好{{b.m.n}}
    <br>
    <input type="text" v-model="b.m.n">
  </div>
  <button onclick="add()">加一</button>
  <script src="/xuni/bundle.js"></script>
  <script>
    var vm = new Vue({
      el: '#app',
      data: {
        a: 10,
        b: {
          m: {
            n: 50
          }
        }
      },
      watch: {
        a() {
          console.log('aaa');
        }
      }
    })
    function add() {
      vm.b.m.n++
    }
  </script>
</body>

</html>